He once touched on the impetus of his artistry in a graduation address in 1969 at the Royal Academy of Music in Toronto. “I sang because I had to,” he said. Singing, he explained, was “an absolute necessity, fulfilling some kind of emotional and even perhaps physical need in me.”

Vickers was sometimes accused of pushing too far, of breaking the mould of the roles he played: Laca in Jenůfa, Alvaro in La forza del destino, the uninhibitedly promiscuous Nerone in Monteverdi’s L’incoronazione di Poppea. And Tristan. Though he was a practised Wagnerian, proud to have been Knappertsbusch’s last Parsifal, Vickers mistrusted Wagner in general and Tristan in particular – ‘a glorification of Wagner’s own immorality’ as he put it. Robin Holloway summed up the terribilità of Vickers’s Tristan when he wrote of the Third Act of the Karajan recording: ‘There is no doubt whatsoever about the stature of this unique tour de force, but it remains an extreme – something unique as if the story were, just this once, literally true [my emphasis].’